"ID theorists discern positive evidence of a designer’s hand at work in that history."

Discern all you want.  You need evidence to make it in science, not just incredulity.  What discoveries support ID?

"The identity of the designer, of course, is not a scientific question but a philosophical or theological one."

What?  Why isn't it a scientific question?  Anything that acts on the natural world would have natural effects.  If we were put here by, say, aliens, we could look for tools left behind, structures, coded messages in our DNA, discontinuities in DNA from gene splicing and other genetic manipulation etc etc.  Saying you can't ID the IDer is nothing but a cop-out for your own lack of evidence that there is one at all, or that there is any phenomenon that indicates anything other than naturalistic processes on Earth unfolding over billions of years.